Piezoelectric materials are used in a variety of sensors and actuators. Piezoelectric materials convert mechanical energy to electrical energy and vice versa. For instance, if pressure is applied to a piezoelectric crystal, an electrical signal is generated in proportion thereby producing the function of a sensor. Generation of an electrical signal in response to an applied force or pressure is known as the “primary piezoelectric effect”. Similarly, if an electrical signal is applied to a piezoelectric crystal, it will expand in proportion as an actuator. Geometric deformation (expansion or contraction) in response to an applied electric signal is known as the “secondary piezoelectric effect”. Whether operated as a sensor or actuator, electrically-conductive electrodes must be appropriately placed on the piezoelectric crystal for collection or application of the electrical signal, respectively. Therefore, a piezoelectric sensor (actuator) consists nominally of a) a portion of piezoelectric material, and b) electrically-conductive electrodes suitably arranged to transfer electrical energy to (from) an external power source.
Piezoelectric materials have been utilized to create a variety of simple sensors and actuators. Examples of sensors include vibration sensors, microphones, and ultrasonic sensors. Examples of actuators include ultrasonic transmitters and linear positioning devices. However, in most of these examples, bulk piezoelectric material is machined and assembled in a coarse manner to achieve low-complexity devices.
Generally, vibrating rotational rate sensors are based on the Coriolis effect. Existing Coriolis devices generate a primary vibration motion along a first axis direction and measure the amplitude of secondary vibration along a second axis direction, said first and second axis directions being perpendicular (orthogonal) to each other. According to the Coriolis effect, the amplitude of secondary vibration is proportional to the rate of rotation around a third axis direction, said third axis direction being perpendicular (orthogonal) to both said first and second axis directions. In existing vibrating rate sensors, the amplitude of secondary vibration is measured as an indicator of rotational rate. Sensors convert the amplitude of secondary vibration into an electrical signal proportional to the rotational rate. However, the amplitude of secondary vibration is also responsive to temperature, vibration, package strain, electromagnetic interference and other undesirable effects that corrupt the rate sensor data.
The existing vibrating rotational rate sensors rely on single-ended actuation and sensors to produce and measure the vibrational motion. Single-ended sensors are generally responsive to temperature, vibration, package strain, electromagnetic interference and other undesirable effects that corrupt the sensor data. Single-ended actuators provide less accuracy in controlling the vibrational motion.
Therefore, there is a need for an improved piezoelectric rate sensor device and method.